When electronic circuits communicate with each other, electrical or galvanic isolation of the electronic circuits is sometimes essential to reduce or eliminate noise in the communication stream or to prevent malfunction of or damage to either electronic circuit due to a voltage spike from the other electronic circuit. Various types of galvanic isolation techniques have been created for various applications. Such isolation techniques may involve capacitive, inductive or optical isolation.
Capacitive isolation uses one or more capacitors to couple data signals across a capacitive barrier between electronic circuits. A time varying electric field transmits information across the capacitors. A dielectric material between the plates of the capacitor forms the isolation barrier.
An example capacitive isolation technique is illustrated with a circuit structure 100 in FIG. 1. The technique splits the different electronic circuits between separate dies 101 and 102 to ensure isolation between the circuits. A plate capacitor 103 on the first die 101 is connected via a bond wire 104 to the second die 102. In this manner, the electric coupling with galvanic isolation occurs within the plate capacitor 103. This technique requires a split paddle assembly package wherein the two dies 101 and 102 are mounted on separate carriers 105 and 106, respectively, within an overall IC package to further ensure electrical isolation. However, a generally weak signal and a large inductance of the bond wire 104 limit the speed of communication between the electronic circuits of the two dies 101 and 102.
An alternative solution incorporates the two circuits onto a single die, but on an isolating substrate, such as sapphire. The single die structure does not need a bond wire between the circuits, which helps reduce parasitic inductance, so the communication speed between the circuits can be enhanced. However, sapphire substrates are generally undesirable due to being relatively expensive.